Test probe for measurement of moisture in structural material

ABSTRACT

The invention relates to a test probe (1) primarily intended to be applied in structural material (2) during the production and/or building stage or when water damage has occured in a building and in which moisture measurement can be done undisturbed from outer factors in following the drying out process of built in moisture or other inconvenient, supplied moisture which can cause troubles in the form of mold and/or damages caused by putrefaction, as well as damages on floor coverings and other structural elements. The test probe (1) comprises an active part (3) of a hygroscopic material which is enclosed in an outer, mechanical cover (4), said cover has that property to allow passage of water steam, but prevents passage of water in liquid.

BACKGROUND OF THE INVENTION

The present invention relates to a test probe which primarily isintended for being applied in structural materials during productionand/or building activity or when water damage has occured in a buildingand by which test probe moisture measurement can be performedundisturbed from outer factors in following of the drying up process ofbuilt in moisture or other not suitable, supplied moisture which cancause inconveniences in the form of mould and/or damage caused byputrefactions, as well as damage of floor coverings and other structuralelements.

At present the problem of building moisture within the building sectoris a scourge which besides the fact that it causes many practicalproblems, e.g. origin of mould and other "sick house" problems, is thesource of very wide and in itself unnecessary increases in prices. Todaythe idea of the used technique to reveal the departure of buildingmoisture is that you drill a hole in the building element in question toa desired depth, where you want to determine the moisture level. Atransmitter is then inserted into the hole, by aid of which you can readon an after-connected instrument the temperature and the relativehumidity of the material (RF %). Several types of transmitters are usedand for all concern the unexactness proportionately is as large as about±3-5% RF. The technique of this measuring method is relativelycomplicated and requires good knowledge in technics of measurement,which only in exceptional cases exsists within the building sector.

The object of the present invention is to provide a test probe, by whichthe problems exsisting in the transmitter which now are present on themarket have been eliminated. The distinguishing features of theinvention are set forth in the claims mentioned below.

Thanks to the invention, one has now achieved a test probe which in anexcellent way fulfils its purpose, and at the same time, is both cheapand easy to produce. By aid of the test probe according to the inventionit is possible to already from the beginning, i.e. from the stage ofproduction of a structural work, to follow the development of the dryingup of built in moisture, commonly called as building moisture, in mostof the building elements, that a structural work consists of. Furtherthe invention decreases the necessary knowledge of techniques ofmeasurement, which are required up to a minimum and minimizes sources oferrors which otherwise can occur principally in that its active part isable to be applied in the building element itself during the productionstage on the building site. This fact makes it possible to measure themoisture state undisturbed by outer factors, where you really want to doit and whenever you want. Both the actual test probe as well as theindicating instrument are in fact much cheaper than the set of apparatuswhich today are present on the building market intended for similarapplications. The test probe according to the present invention has anapplication range of a high quality in determination of actual moisturestage at a low price.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described below by aid of a preferredembodiment with reference to the drawings enclosed, in which

FIG. 1 schematically illustrates a test probe according to the inventionwhich is cast into a structural work and

FIG. 2 schematically illustrates another embodiment of a test probeaccording to the invention in a condition cast into its position.

DESCRIPTION OF THE INVENTION

As illustrated in FIG. 1 a preferred, first embodiment of a test probe 1according to the present invention consists of such a formation which isfixable in a structural material 2 during the production stage. It is,in other words, possible to be cast into e.g. concrete directly which isunique within the moisture measurement range. The test probe 1, whichhas such a quality that it can absorb and emit moisture in steam phasebut not in liquid phase, includes an active part 3 consisting of ahygroscopic material, said part is enclosed in an outer, mechanicalcover 4. The test probe 1 has that quality owing to that the cover 4consists of an expanded plastic designed in such a way that water vapourcan pass through it, but not water in a liquid phase. The cover 4 isalso intended to prevent a break down of the active part 3 of the testprobe 1, which is exposed to pressure during casting into the concrete.The mechanical cover 4 is continuous as to its formation and is providedwith a supporting means 7 in one end of the same in the form of threadedwashers 8 for tightening of the test probe 1 in a position fixing means9 for a temporary fixing of the same in connection with concretecasting. The position fixing means 9 is also threaded, and therefore canbe moved within the washers 8 to fix the cover 4 between the means 9.Alternatively, the means 9 can be fixed in place, and the washers 8 canbe moved along the means 9 to fix the cover 4 between the washers 8.

The active part 3 of the test probe 1 which consists of a hygroscopicmaterial comprises in the example described a round bar of wood having adiameter of about 6 mm. This material adjusts its relative humidity RF %to the relative atmospheric humidity RF % of the ambient material. Twounisolated electrodes 5 and 6 are inserted into the active part 3thereby making it possible to read the actual relative atmospherichumidity RF % of the test probe 1. These electrodes 5,6 are stuck intothe active part 3 of the test probe 1 a distance, which in the exampleillustrated amounts to about 3-6 times the diameter of the active part3. Those parts of the electrodes 5,6 which extend from the test probe 1and through the concrete 2 and further to a resistance meter 20 areisolated. On the electrodes 5,6 the electrical resistance which occursbetween them, is measured, at actual moisture level. The resistance isindicated with a conventional resistance meter at different moisturelevels.

Since the magnitude of the resistance also is dependent of thetemperature at the measuring place, it is measured by a temperatureindicator in the form of a thermistor 10 which is situated between theactive part 3 of the test probe and the mechanical cover 4 and which isconnected to a measuring equipment not illustrated in the drawing by acable 12. In reading a temperature other than 20° C., the resistancereading is compensated (corrected) by aid of a micro-processor 22.

The instrument also can be equipped with an indicator which indicatesthe temperature measured in °C. The conversion of the temperaturecorrected resistance reading to relative humidity RF % occurs in that aresistance values for moisture between 75-97% RF reference are fed intosaid micro-processor. The temperature corrected resistance reading iscompared to the resistance values fed into the micro-processor to obtainthe relative humidity associated with the temperature correctedresistance reading.

In FIG. 2 is illustrated a modified embodiment of the test probe 1according to the present invention. Here it is primarily the fixingitself of the test probe 1 in place which is different. Otherwise theconstruction almost corresponds to that test probe illustrated inFIG. 1. However, the supporting means 7 is here formed as a means ofattachment 11. The electrodes 5 and 6 and the transmitter cable 12extended through this from the thermistor 10 by an opening 13. A roundbar 14 is by its threading into the attachment means 11 intended both tounload said cables 5,6 and 12 from tension and to fix the test probe 1during its casting into the structural material 2 which consists ofconcrete.

I claim:
 1. A test probe assembly applied to structural materialcharacterized in that a test probe is applied within the structuralmaterial and comprises an active part (3) consisting of a hygroscopicmaterial, mostly enclosed in an outer mechanical cover (4) having aquality of allowing passage of water vapor but not liquid water and saidcover (4) consists of a housing of expanded plastics resistant topressure so as to allow casting of the test probe (1) into thestructural material, at least two unisolated electrodes (5, 6) providedin the active part (3), said electrodes in an isolated state extendingfrom the test probe (1) through and out from the structural material (2)and to a resistance meter means for measuring electrical resistancewhich is present in the active part (3) between the electrodes (5,6),and at least one thermistor (10) located between the active part (3) andthe mechanical cover (4) and which by a connecting cable is connected toa microprocessor programmed to compensate the resistance reading as afunction of a measured temperature and convert said temperaturecompensated resistance reading to relative humidity (RF %) by comparisonto reference resistance values for humidity between 75-97% RF in themicro processor, and an indicator to display the value of the relativehumidity determined.
 2. A test probe assembly according to claim 1,characterized in that the active part (3) consists of a round bar ofwood having a length of about 3-6 times its diameter.
 3. A test probeassembly according to claim 2, characterized in that the mechanicalcover (4) is elongated and has one end provided with a supporting means(7) in the form of a threaded washer (8) movable relative to a fixingrod (9).
 4. A test probe assembly according to claim 3, characterized inthat the round bar of wood has a diameter of 6 mm.
 5. A test probeassembly according to claim 2, characterized in that the mechanicalcover (4) has one end fixed to a supporting means (7) in the form of anattachment means (11), through which the electrodes (5,6) and theconnecting cable (12) from the thermistor (10) extend via an opening(13) out to and through the structural material (2), and in saidattachment means (11) a position fixing means in the form of a round bar(14) is threaded, both to unload the electrodes and the connecting cable(12) in the opening (13) in tension and also to fix the test probe (1)during its casting into the structural material (2).
 6. A test probeassembly according to claim 5, characterized in that the round bar ofwood has a diameter of 6 mm.
 7. A test probe assembly according to claim2, characterized in that the round bar of wood has a diameter of 6 mm.8. A test probe according to claim 1, characterized in that theunisolated electrodes (5,6) extend into the active part (3) a distance,which is at least 1/3 of its total, effective length.
 9. A test probeassembly according to claim 8, characterized in that the mechanicalcover (4) is elongated and has one end provided with a supporting means(7) in the form of a threaded washer (8) movable relative to a fixingrod (9).
 10. A test probe assembly according to claim 8, characterizedin that the mechanical cover (4) has one end fixed to a supporting means(7) in the form of an attachment means (11), through which theelectrodes (5,6) and the connecting cable (12) from the thermistor (10)extend via an opening (13) out to and through the structural material(2), and in said attachment means (11) a position fixing means in theform of a round bar (14) is threaded, both to unload the electrodes andthe connecting cable (12) in the opening (13) in tension and also to fixthe test probe (1) during its casting into the structural material (2).11. A test probe according to claim 1 characterized in that themechanical cover (4) is elongated and has one end provided with asupporting means (7) in the form of a threaded washer (8) movablerelative to a fixing rod (9).
 12. A test probe assembly according toclaim 1 characterized in that the mechanical cover (4) has one end fixedto a supporting means (7) in the form of an attachment means (11),through which the electrodes (5,6) and the connecting cable (12) fromthe thermistor (10) extend via an opening (13) out to and through thestructural material (2), and in said attachment means (11) a positionfixing means in the form of a round bar (14) is threaded, both to unloadthe electrodes and the connecting cable (12) in the opening (13) intension and also to fix the test probe (1) during its casting into thestructural material (2).
 13. A test probe assembly according to claim 1,wherein the structural material is concrete.